1. Field
The teachings in accordance with the exemplary embodiments of this present disclosure generally relate to a display device, and more particularly to a display device configured to improve legibility, color reproduction range and power consumption.
2. Background
Organic electroluminescent devices, for example, organic electroluminescent diodes, are provided with a thin film containing a light-emitting organic compound between an anode and a cathode. By injecting holes and electrons from the respective electrodes, excitons of the light-emitting organic compound are generated. When these excitons return to a ground state, the organic electroluminescent devices irradiate light.
Recent developments in organic electroluminescent devices have been very significant. Characteristic examples of such developments include high brightness at low applied voltages, more diversity in emission wavelengths, wider viewing angle, rapid response, greater color reproduction range, and the ability to produce thinner and lighter light-emitting devices. As a result of these developments, a broad range of possible applications to illumination fields using the organic electroluminescent devices has been briskly waged.
FIG. 1 is a schematic view illustrating a stacked structure of an organic electroluminescent device according to prior art, where the device is stacked with a substrate (11), an anode (12) which is a transparent electrode, an organic light emitting layer (13), a cathode (14) which is a reflective electrode and a protective film (15) in that order.
A full color spectrum in the organic electroluminescent device is realized by having pixels that separately emit red (R), green (G), and blue (B) colors, or by white color. At this time, in order to express a desired color, a plurality of organic electroluminescent devices configured to emit light of different wavelengths is coupled for use.
Korea Laid-open Patent Application No. 2007-0008071 discloses a technique in which each width of organic light emitting structures is vertically stacked at a predetermined level to equalize an area of RGB sub-pixel and an area of pixel, whereby luminance can be increased and pixelization can be eased. However, according to this structure, light generated from a sub-pixel positioned at a middle section is reflected from a sub-pixel positioned at a distal end to be emitted to the outside and to disadvantageously reduce the light efficiency. Another disadvantage is that light radiated from the organic light emitting structures is reduced in legibility under a bright environment such as the sun light.
Meanwhile, although power consumption can be greatly reduced by radiating light using a reflective light in case of a reflective pixel used for electronic paper, disadvantage is that the color reproduction range is low, and it is difficult to use at night.